Psu 12v 5v touched

It sounds as though you have been extremely lucky. As you may know, the PSU provides several different power rails at different voltages to supply the hardware and components in your system. The +5V and +3.3V rails supply much of the logic circuitry, whereas the +12V rail supplies power to the various motors (fans, HDDs, optical drives) and the voltage regulator for the CPU. An accidental short between the +12V rail and either of the other two rails can cause severe damage to your system, even if the short circuit is of a very brief nature.

As I said, you have been very fortunate that the system shutdown instantly and that no apparent damage was caused, although I would definitely not recommend repeating just in case this was a fluke. That said, I would keep an eye on your system for the next few days or so to see whether you get any problems (including BSODs) that could be attributable to this episode.

Quite possible, although it is still possible that you have caused some damage to your motherboard given that some components may have been subjected to a voltage that is over double the normal level (12V versus 5V), even if only for a split second. As I said previously, you need to monitor your system for any signs of abnormal behaviour.

stomper I think you dodged a bullet.

You're welcome, stomper. :)